1. Field of the Invention
The present invention relates to automatic manufacture of stratified structures such as laminated panes.
2. Discussion of the Related Art
Laminated panes used in buildings and transport vehicles, notably as a windscreen, are generally formed of at least one rigid sheet such as a sheet of glass or a sheet of plastic material such as polycarbonate or polymethylacrylate, and at least one sheet of flexible plastic material, of polyvinylbutyral or polyurethane for example, generally used as an intermediate sheet in the case of a structure comprising two rigid sheets.
To make these laminated panes, the sheet or sheets of flexible plastic material are cut initially to the exact shape of the pane or generally to a geometrical shape which is slightly larger and generally described as a blank, and they are stacked with the other elements forming the laminated pane. All of these elements are assembled together by means of an assembly operation which is generally carried out in two stages: the first stage consists for example, of a calendering operation effecting preliminary assembly, followed by a second stage consisting of an autoclave cycle using a high temperature and pressure for producing the final assembly.
The invention relates more particularly to stacking of the flexible sheet with the other elements forming the laminated pane, and the operations associated with it, notably its initial centering in an intermediate position adjacent the stacking station, its transfer to the stacking station and its deposition in the correct position in the stack.
One of the problems encountered in automation of the different operations used for manufacturing laminated panes is the correct positioning in the stack to form the pane.
One solution which has already been suggested consists of precisely arranging the sheets of plastic material one on the other at a fixed and predetermined position called a storage station. In this case the sheet is gripped at that location and it is transferred by a path of constant length to the stacking station for the laminated pane. Unfortunately, sheets of plastic material of polyvinylbutyral or polyurethane have at the temperatures encountered in assembly plants a certain tendency to adhere to each other and it is found that at the moment of gripping the upper sheet of the pile the sheet immediately below is also seized temporarily as it is more or less adhered, and it may be displaced from its correct gripping position. The resulting displacement of the sheet is then transferred to the stacking station and the stacking will not be correct.